II.) Deciding to Compress an existing tables or not

We would like to evaluate the amount of compression we would get before we decide to compress a table. We can do a "create table as select" as above, but this would not be feasible for very large table.

Oracle provides a handy procedure to estimate the compression we would get on an existing table. The procedure is called DBMS_COMPRESSION.GET_COMPRESSION_RATIO. DBMS_COMPRESSION.GET_COMPRESSION_RATIO cannot be used to find the ratio for BASIC compression.

Note: Please create a tablespace which you would use for this testing, as this procedure can use a lot of space for getting the compression ratio. We would not want to use our application or users tablespace as it would be difficult to retrieve this space back. You can create a tablespace named SCRAP and then drop it after the evaluation is done.